Nonwoven fabrics are used in a variety of applications such as garments, disposable medical products, diapers and personal hygiene products. New products being developed for these applications have demanding performance requirements, including comfort, conformability to the body, freedom of body movement, good softness and drape, adequate tensile strength and durability, and resistance to surface abrasion, pilling or fuzzing. Accordingly, the nonwoven fabrics which are used in these types of products must be engineered to meet these performance requirements.
One such type of nonwoven fabric includes fabrics that include elasticity. One approach which has been taken to providing such elastic properties in a composite nonwoven fabric involves forming and stretching an elastic web, then bonding a gatherable web to the elastic web, and relaxing the composite. An obvious limitation of this approach is having to form the composite in the tensioned state. This requires additional equipment and control systems. Examples of this process are Mormon, U.S. Pat. No. 4,657,802, where it is disclosed that a composite nonwoven elastic is made by first stretching an elastic web, forming a fibrous nonwoven gatherable web onto the stretched elastic nonwoven, joining the two together to form a composite structure, then allowing the composite to relax. In Collier, et al., U.S. Pat. No. 5,169,706, it is disclosed that a composite elastic material having a low stress relaxation is formed between an elastic sheet and a gatherable layer. In Daponte, U.S. Pat. No. 4,863,779, a composite is disclosed which involves first tensioning the elastic web to elongate it, bonding at least one gatherable web to the elastic web, and relaxing the composite immediately after bonding, so that the gatherable web is gathered between the bond points.
Another approach to imparting elastic properties to a composite nonwoven fabric is with a so-called “zero-strain” stretchable laminate. A “zero-strain” stretchable laminate refers to a fabric in which at least two layers of material, one elastic, the other substantially inelastic, are secured to one another along their coextensive surfaces while in a substantially untensioned state. The fabric is subsequently subjected to mechanical stretching. The inelastic layer typically fractures or extends, thus permanently elongating the inelastic layer and producing a composite fabric with elastic properties. This lamination and stretching process is advantageous in that utilizing elastic in an unstretched condition is easier and less expensive than stretched elastic used in traditional processing operations. However, one problem which has existed with presently available “zero-strain” stretchable laminates is surface abrasion. The mechanical stretching either fractures or disrupts the fibers within the substantially inelastic component of the “zero-strain” laminate, and as a result, the fibers detach and are susceptible to linting and pilling. In addition, such fracturing or detachment causes a noticeable loss in fabric strength.
Another technique involves the use of extensible nonwoven fabrics that are elongated by application of a tensile stretching force. However, it has been found that fibers having good extensibility without sacrificing drapeability and abrasion resistant are difficult to produce. Accordingly, there still exists a need for highly extensible fabrics with improved feel and abrasion resistance.